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Re: Joists & Adding Roof Mechanical Unit

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Just bolt the new pipe stanchion in place with end plates already
welded to it.  Use 4 bolts so it is clamped in place--
no welding.
Gary

On 29 Oct 2004 at 12:39, richard lewis wrote:

> This sounds like it might be a feasible alternative.  So if I
> understand this, the roof would be opened at the locations of the pipe
> post.  The pipe post base would be welded to the joist from the top. 
> Then the roof is closed again.  I can then sit a "curb" on top of the
> posts.  This would minimize disruption of the office space below, but
> I'm sure there still would be some welding sparks dropping.  At least
> the equipment is on the roof.
> 
> Did I understand you correctly here?
> 
> Thanks.
> 
> Rich
> 
> On Fri, 29 Oct 2004 13:31:19 -0400 "Jordan Truesdell, PE"
> <seaint(--nospam--at)truesdellengineering.com> writes:
> > Disclaimer: I'm used to using pipe columns and pitch pockets for
> > rooftop curbs.  Can you afford a three-tier curb system - two rails
> > over the panel points, perpendicular rails on top of that to support
> > the curb rails at the proper spacing?  It's more steel tonnage, but
> > it will get you to the 
> > 
> > bearing points of the trusses without having mess around in the
> > ceiling.
> > 
> > At 10:49 AM 10/29/2004 -0500, you wrote:
> > >I have an existing roof structure where the owner wants to add a 
> > rooftop
> > >mechanical unit.  The unit weighs about 3,000 lbs.  The existing 
> > roof
> > >joists are 24H9.  I checked the roof joists and supporting girders 
> > and
> > >they are fine to support the additional load.
> > >
> > >I have a detailing question.  I know this has been done many times 
> > so I
> > >am hoping someone will share their experience with me.  I plan to 
> > ask
> > >that the unit be placed on a continuous curb that runs 
> > perpendicular to
> > >the roof joists.  My question has to do with the curb bearing on 
> > the roof
> > >joist.  First, I assume the curb will bear directly on the deck.  
> > No roof
> > >penetrations are required.  The roof deck is corrugated decking as 
> > the
> > >joists are about 2 feet on center.  The curb will run parallel to 
> > the
> > >deck flutes.  It is typical to just run a wood plate on top of the 
> > deck
> > >to support the curb?  The curb will be a structural curb that 
> > spans
> > >between joists.  Next, in new construction when the concentrated 
> > load is
> > >put on a joist top chord at a place other than a panel point an 
> > angle is
> > >welded from the top chord down to the bottom panel point.  The 
> > space
> > >below is occupied by office space and to weld a few angle struts 
> > would be
> > >very difficult on innocent tenants.  Is there another detail that 
> > might
> > >not involve filed welding?  Would I be able to skip the angle strut
> > >
> > if
> > e maximum possible point load from the curb were under 1,000 lbs?
> > >
> > >
> > >Thanks for your help.
> > >
> > >Rich
> > >
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